Combustion apparatus



Aug. 27, 1968 R. s. HALL ETAL COMBUSTION APPARATUS Filed Aug. 14, 195.9

3 Sheets-Sheet 1 ATTORNEY 1968 R. s. HALL ETA; 3,398,538

COMBUSTION APPARATUS Filed Aug. 14, 1959 3 Sheets-Sheet 2 1%; Mil/11! TOPS (ya/ewe? oa /yrs A 7' TOR/V5 Y 7, 1968 R. s. HALL ETAL 3,398,538

COMBUSTION APPARATUS Filed Aug. 14, 1959 5 Sheets-Sheet 5 fil arewce [Qua er;

ATTORNEY United States Patent 3,398,538 COMBUSTION APPARATUS Russell S. Hall, John R. Patten, and Clarence Bowers,

Indianapolis, Ind., assignors to General Motors Corporation, Detroit, Mich., a corporation of Delaware Filed Aug. 14, 1959, Ser. No. 833,884

7 Claims. (Cl. 60267) Our invention relates to combustion apparatus particularly suited for the use of vaporizable fuels, which may be used in various environments. The apparatus is particularly suited to fuels which are gases or vapors under normal atmospheric conditions, but which are stored in liquid form before use. Certain portions of the system are well suited to gaseous fuels which need not be vaporized. The preferred embodiment of the invention is illustrated and described herein in an application to a jet propulsion engine.

The combustion apparatus of the invention is adapted to vaporize a liquid fuel, utilizing the expanding Vapor to drive a turbine which powers an air compressor. The vaporized fuel discharged from the turbine is mixed with air supplied by the compressor, and combustion is effected in a combustion apparatus which operates on a fuel-rich basis so that it discharges a hot mixture of fuel and combustion products. This mixture flows through a heat exchanger to vaporize the fuel entering the turbine and thus provide the vapor which drives the turbine. A part of the air delivered by the compressor bypasses the combustion apparatus and is mixed with and burns the fuel of the fuel-rich mixture discharged from the heat exchanger. The resulting hot combustion products may be used for various purposes and, as illustrated, are employed to provide a propulsive jet. It will be understood that the foregoing is merely a very general introduction to the nature of the invention, which will be made clear by the succeeding detailed description.

The principal objects of the invention are to provide an improved combustion apparatus particularly suited to gaseous or vaporizable fuels; to provide a combustion system adapted to provide a jet of hot combustion products but which does not require a high temperature turbine; to provide combustion apparatus particularly suited to fuel-rich combustion; to provide a compact, efiicient combustion system; and to provide novel and particularly effective combustion apparatus for such a system.

The preferred embodiment of the invention is illustrated in the accompanying drawings, of which FIGURE 1 is an axonometric view of a vapor cycle jet engine with parts cut away and in section.

FIGURE 2 is a partial sectional view of the inlet end of the combustion apparatus taken on a plane containing the axis of the engine as indicated by the line 2-2 in FIGURE 3.

FIGURE 3 is a partial transverse sectional view of the inlet end of the combustion apparatus taken on the plane indicated by the line 33 in FIGURE 2.

FIGURE 4 is a fragmentary sectional view of a mixer taken on a plane containing the axis of the engine.

Referring first to FIGURE 1 for a general description of the organization of the combustion apparatus and the jet engine in which it is included, the engine includes from front to rear an inlet section 10, a compressor 11, a diffuser or transition section 12, combustion apparatus 13, a heat exchanger 14, a mixer 16, secondary combustion apparatus 17, and an exhaust duct 18 within which may be mounted a variable jet nozzle (not illustrated). Part .of the air discharged by the compressor flows through the combustion apparatus 13 and part flows through a bypass duct 19 around the combustion apparatus to the mixer 16 and combustion apparatus 17. Liquid vaporizable fuel is 3,398,538 Patented Aug. 27, 1968 supplied to the engine by any suitable means adapted to control the flow, indicated schematically as a pump 21, and through annular fuel manifolds 22 which conduct it to numerous radial heat exchange tubes 23 extending from the outer to the inner boundary of the heat exchanger 14. Fuel is heated and vaporized in the heat exchanger, and the vaporized fuel flows through a turbine entrance annulus or nozzle box 24 inside the heat exchanger into an axial-flow turbine 26. The turbine 26 is driven by the expansion of the vapor and drives the compressor 11 through a shaft 102 (FIG. 3) mounted in a housing 27. The turbine exhausts into a plenum chamber 28 within the diffuser section 12 and the fuel is conducted from the plenum chamber to the inlet of the combustion apparatus 13 by a number of circumferentially spaced recurved fuel ducts 29.

The inlet section 10 of the compressor comprises an outer wall 31, an inlet spike 32, and inlet vanes 33 mount ing the spike. The compressor 11 comprises a main compressor having a number of stages of rotary blading 34 and stationary blading 36, the rotary blading being mounted on a rotor structure 37. The outlet of the compressor is divided between two annular ducts, an outer or bypass duct 19 previously referred to, the forward portion of which is defined by the outer wall or case of the diffuser, and a conical intermediate wall 38. An inner diverging diffusing duct 39 is defined between the wall 38 and an inner wall 41. An additional compressor stage 42 operates in the duct 39. Struts 43 extending from the inner walls support the compressor-turbine shaft arrangement.

The turbine 26 comprises a rotor 44 on which are mounted a number of rows of blades and a case 46 mounting a number of rows of stator blades. The case 46 is double-walled. The combustion apparatus 13 is bounded by a cylindrical outer wall or case 47 and a cylindrical inner wall 48 mounted around the turbine case. The portion of the bypass duct to the rear of the diffuser section 12 is defined between an outer engine case 49 and the outer combustion apparatus case 47.

The combustion apparatus also comprises an annular outer shroud 51 and an annular inner shroud 52 which define between them a combustion space 53. An annular fuel passage 54 (see also FIG. 2) is defined between the wall 47 and shroud 51 and a second annular fuel passage 55 is defined between the wall 48 and shroud 52. The shrouds 51 and 52 may be composed of a number of annular sections connected by corrugated or zig-zag strips 57 welded to the adjacent ends of adjacent sections. This is known combustion liner structure. The shrouds 51 and 52 diverge from each other toward the outlet or discharge end .of the combustion chamber, and the passages 54 and 55 correspondingly converge in this direction. The forward ends of the shrouds may be supported and located by circumferentially spaced brackets or clips 58 fixed to structure at the forward end of the combustion apparatus, and the rear ends may be suitably supported by means not illustrated.

Means are provided at the inlet end of the combustion apparatus within the intermediate wall 38 to conduct the vaporized fuel from the turbine exhaust chamber 28 and air from the diffuser 39 into the combustion apparatus. As previously stated, a number of circumferentially spaced recurved fuel ducts 29 are provided to conduct the fuel. Referring particularly to FIGS. 2 and 3, each of these ducts 29 is of rectangular or box section and curves from a radial direction at its connection to the plenum chamber to an axial direction at its outlet. Each duct 29 comprises a radially outer wall 61, an inner wall 62, and side walls 63. A considerable number of substantially arc turning vanes 64 are provided, extending from one side wall 63 to the other, to promote smooth fiow of the fuel and prevent improper distribution at the outlet of the fuel duct. The discharge ends of the ducts 29 are interconnected by two annular fuel manifold structures 66 and 67, the former being at the outer edge and the latter at the inner edge of the duct. As will be more apparent from FIGURE 2, each of these manifolds is of box section and is divided by a ring 68 into two portions, an outer fuel manifold 69 aligned with the passage 54 or 55 and an inner fuel manifold 71, the wall 68 of which is substantially coincident with the adjoining shroud 51 or 52. Openings 73 and 74 in the forward walls of these manifolds permit entrance of fuel from the ducts 29. The forward wall is closed where it crosses the spaces between the ducts 29.

Elongated discharge slots 76 which form almost a complete annular opening discharge fuel into the passages 54 and 55. Similar elongated fuel discharge slots 77, which are of smaller width and, therefore, area, discharge fuel into the combustion space 53 immediately adjacent the shrouds 51 and 52 to provide a fuel fiow or cooling film along the inside surfaces of the walls. Since the fuel after expansion through the turbine is cooler than the compressed air (which may be heated by ram compression as well as by the compressor 11, 42), the circulation of fuel along both sides of the shrouds 51 and 52 provides considerable cooling of the shrouds and minimizes damage to the shrouds from overheating. As will be apparent, the clips 58 are welded to the rear walls of the manifold structures 66 and 67.

The greater part of the fuel delivered by the ducts 29 is discharged from the open ends of the ducts through the areas indicated as 81, thus providing a number of axially directed fuel streams extending from one shroud to the other. As illustrated, there are twenty-four of the ducts 29 and, therefore, twenty-four openings 82 between the ducts through which air flows from the dilfuser 39 into the inlet end of the combustion space. There are thus a number of cores of air surrounded by fuel entering through entrances 77 and 81.

Preferably, the fuel and air are introduced at different velocities so that the parallel streams of fuel and air mix thoroughly because of the dilferent velocities and rapid eflicient combustion is effected. With hydrogen, which is a preferred fuel, the velocity of the fuel may be about three times that of the air. The pressures of the two fuels are of the same order of magnitude and the Mach number of flow is about the same. It should be remembered that the combustion apparatus operates on a fuel-rich basis; that is, with an excess of fuel over the stoichiometric ratio. The fuel is used to blanket and cool the shrouds bounding the combustion space. Fuel from the passages 54 and 55 enters the combustion space 53 at each of the annular film cooling gaps defined by the corrugated strips 57. The gas discharged from the combustion apparatus is a hot mixture of fuel and combustion products, the combustion products being the products of combustion of the fuel plus the non-combustible gases in the air; the oxygen will be substantially entirely consumed. This combustible mixture flows rearwardly between and around the radial tubes 23 of the heat exchanger 14, vaporizing the fuel and then flows into the mixer 16 mounted within the wall 84 of the exhaust duct portion of the engine.

The mixer provides a structure for mixing the combustible mixture with the compressed air supplied through the bypass duct 19 similar in structure and principle to mixing arrangement for the fuel and air in the inlet end of the combustion apparatus. As indicated most clearly in FIGURE 4, the mixer is defined by a relatively large number of box section ducts 86 for the mixture which are spaced circumferentially from each other and are bounded by outer walls 87 and inner walls 88. The inner wall 88 is preferably annular, but the outer wall 87 is a separate wall for each duct 86 extending from one side wall 89 to the other side wall of the mixture duct. Ducts 91 for the bypass air are bounded by the wall 84 and by inwardly converging walls 92 bridging the gaps between the ducts 86. The combustible mixture and air are discharged in generally parallel interleave d jets into the entrance portion of the secondary combustion apparatus defined between the wall 84 and a tailcone 93 which closes the forward end of the combustion apparatus. A fiameholder 94 comprising the usual V-shaped gutters is mounted in the upstream end of the combustion apparatus 17 to anchor the flame.

Suitable ignition means for the combustion apparatuses .13 and 17 (not illustrated) may be provided. Struts 96 extending inwardly from the mixer 16 provide a support for the rear end of the turbine rotor 26. Referring to FIGURE 3, the turbine exhaust plenum chamber 28 is bounded by an outer wall 97 from which the fuel ducts 29 extend and by an inner wall 98. Struts 99 support a shaft housing 101 within the plenum chamber through which the shaft 102 connecting the turbine to the compressor extends.

The operation of the engine will presumably be clear to those skilled in the art from the foregoing,-but may be reviewed briefly. To start the engine gaseous fuel may be'supplied from a source of such fuel under pressure. The expanding gaseous fuel drives the turbine 26 and flows into the combustion apparatus 13. Operation of the turbine drives the compressor 11 to force air into the combustion apparatus. A suitable igniter initiates combustion and the hot combustion products flow rearwardly. As soon as the heat exchanger 14 is heated, liquid fuel may be supplied by suitable means. The operation of the engine remains essentially the same, except for the added feature of vaporization of the fuel. In normal operation, the fuel is in excess relative to the air in combustion apparatus 13 and the unburned fuel is consumed in the combustion apparatus 17 by the air supplied through the bypass duct 19. If the combustion apparatus is embodied in a jet engine as shown, the resulting hot combustion products may form a propulsive jet. In this case, a variable propulsive jet nozzle (not illustrated) may be provided, as is customary.

It will be understood that the rotating machinery such as the turbine and compressor and shafting connecting them have not been described in detail since these may follow standard practice, and the details of structure of these are not material to the invention.

It will be apparent that the combustion apparatus described and illustrated is suitable for use with gaseous fuel which is supplied to the apparatus is the gaseous state, in which case the heat exchanger for vaporizing the fuel may be omitted. Also, the combustion apparatus 13 may be used independently of the presence or absence of a second combustion apparatus 17.

While the organization of the combustion apparatusincluding the turbine and compressor is believed to be a significant part of the invention, it will also be realized that the part of the apparatus in which combustion takes place may be used with means for supplying the fuel and air other than those illustrated and such supplying means may be physically remote from the combustion apparatus itself. However, the compact concentric arrangement shown in FIGURE 1 is particularly suited to certain purposes.

Reference to gaseous fuel in the succeeding claims is intended to include both gases and vapors, as distinguished from liquid or solid fuels.

The adavntages of the invention in providing a compact, elficient combustion apparatus or combustion system will be clear to those skilled in the art. The invention provides a compact machine for handling gaseous fuels and provides combustion apparatus for such fuels which is of small dimensions relative to the energy release rate, and which is adequately cooled by the fuel to promote reliability and endurance.

The detailed description of the preferred embodiment of the invention to explain the principles thereof is not to be considered as limiting or restricting the invention,

as many modifications may be made within the scope of the invention by the exercise of skill in the art.

We claim:

1. A combustion system for vaporizable fuel comprising, in combination, means for supplying liquid fuel, an annular heat exchanger for vaporizing the fuel, a turbine supplied with vaporized fuel by the heat exchanger and driven thereby, an annular axial-flow combustion apparatus including outer and inner annular walls disposed around the turbine, mutually circumferentially spaced recurved fuel ducts connecting the outlet of the turbine to one end of the combustion apparatus, the heat eX- changer being disposed at the other end of the combustion apparatus for flow of mixed fuel and combustion products therethrough, an air compressor driven by the turbine, a duct connecting the outlet of the compressor to the combustion apparatus enclosing the said fuel ducts and supplying air to the combustion apparatus through the spaces between the ducts, outer and inner annular shrouds within the combustion apparatus defining a combustion space and defining annular fuel passages between the shrouds and the walls, and two annular fuel manifolds connecting the said ducts with the said annular fuel passages.

2. A combustion system for vaporizable fuel comprising, in combination, means for supplying liquid fuel, an annular heat exchanger for vaporizing the fuel, an annular axial-flow combustion apparatus including outer and inner annular walls, means including mutually circumferentially spaced recurved fuel ducts connecting the outlet of the heat exchanger to one end of the combustion apparatus, the heat exchanger being disposed at the other end of the combustion apparatus for flow of mixed fuel and combustion products therethrough, an air supply means, a duct connecting the air supply to the combustion apparatus enclosing the said fuel ducts and supplying air to the combustion apparatus through the spaces between the ducts in less than stoichiometric ratio to the said fuel, outer and inner annular shrouds within the combustion apparatus defining a combustion space and defining annular fuel passages between the shrouds and the Walls, two annular fuel manifolds connecting the said ducts with the said passages, an annular bypass duct supplied by the air supply means surrounding and bypassing the combustion apparatus, a mixing device interconnecting the bypass duct and the outlet of the heat exchanger to mix the air with the mixture of fuel and combustion products flowing from the combustion apparatus through the heat exchanger, and combustion means downstream of the mixing device for burning the fuel in the bypassed air.

3. A combustion system for vaporizable fuel comprising, in combination, means for supplying liquid fuel, an annular heat exchanger for vaporizing the fuel, a turbine supplied with vaporized fuel by the heat exchanger and driven thereby, an annular axial-flow combustion apparatus including outer and inner annular walls disposed around the turbine, mutually circumferentially spaced recurved fuel ducts connecting the outlet of the turbine to one end of the combustion apparatus, the heat exchanger being disposed at the other end of the combustion apparatus for flow of mixed fuel and com-bustion products therethrough, an air compressor driven by the turbine, a duct connecting the outlet of the compressor to the combustion apparatus enclosing the said fuel ducts and supplying air to the combustion apparatus through the spaces between the ducts in less than stoichiometric ratio to the said fuel, outer and inner annular shrouds within the combustion apparatus defining a combustion space and defining annular fuel passages between the shrouds and the walls, two annular fuel manifolds connecting the said duets with the said passages, an annular bypass duct supplied by the compressor surrounding and bypassing the combustion apparatus, a mixing device interconnecting the bypass duct and the outlet of the heat exchanger to mix the air with the mixture of fuel and combustion products flowing from the combustion apparatus through the heat exchanger, and combustion means downstream of the mixing device for burning the fuel in the bypassed air 4. A combustion system for vapon'zable fuel comprising, in combination, means for supplying liquid fuel, an annular heat exchanger for vaporizing the fuel, a turbine supplied with vaporized fuel by the heat exchanger and driven thereby, an annular axial-flow combustion apparatus including outer and inner annular walls disposed around the turbine, mutually circumferentially spaced recurved fuel ducts connecting the outlet of the turbine to one end of the com-bustion apparatus, the heat exchanger being disposed at the other end of the combustion apparatus for how of mixed fuel and combustion products therethrough, an air compressor driven by the turbine, a duct connecting the outlet of the compressor to the combustion apparatus enclosing the said fuel ducts and supplying air to the combustion apparatus through the spaces between the ducts in less than stoichiometric ratio to the said fuel, outer and inner annular shrouds within the combustion apparatus defining a combustion space open to the fuel ducts for supply of fuel thereto and defining annular fuel passages between the shrouds and the walls, two annular fuel manifolds connecting the said ducts with the said passages and discharging a layer of fuel over the inside surfaces of the shrouds, an annular bypass duct supplied by the compressor surrounding and bypassing the combustion apparatus, a mixing device interconnecting the bypass duct and the outlet of the heat exchanger to mix the air with the mixture of fuel and combustion products flowing from the combustion apparatus through the heat exchanger, and combustion means downstream of the mixing device for burning the fuel in the bypassed air.

5. A combustion apparatus for gaseous fuel comprising, in combination, outer and inner annular walls defining an annular combustion chamber, mutually circumferentially spaced fuel ducts supplying the fuel to the inlet end of the combustion chamber, a first air duct enclosing the said fuel ducts and supplying air to the combustion chamber through the spaces between the ducts, outer and inner annular shrouds within the combustion chamber defining a combustion space and defining annular fuel passages between the shrouds and the walls, and two annular fuel manifolds connecting the said duets with the said annular fuel passages, the fuel ducts having circumferentially spaced fuel outlets extending radially from one said manifold to the other and discharging into the combustion space.

6. A combustion apparatus for gaseous fuel comprising, in combination, outer and inner annular walls defining an annular combustion chamber, mutually circumferentially spaced fuel ducts supplying the fuel to the inlet end of the combustion chamber, a first air duct enclosing the said fuel ducts and supplying air to the combustion chamber through the spaces between the ducts, outer and inner annular shrouds within the combustion chamber defining a combustion space and defining annular fuel passages between the shrouds and the walls, and two annular fuel manifolds connecting the said ducts with the said passages and discharging a layer of fuel over the inside surfaces of the shrouds, the fuel ducts having circumferentially spaced fuel outlets extending radially from one said manifold to the other and discharging into the combustion space.

7. A combustion apparatus for gaseous fuel comprising, in combination, outer and inner annular walls defining an annular combustion chamber, mutually circumferentially spaced fuel ducts supplying the fuel to the inlet end of the combustion chamber, a first air duct enclosing the said fuel ducts and supplying air to the combustion chamber through the spaces between the ducts in less than stoichiometric ratio to the said fuel, outer and inner annular shrouds within the combustion chamber defining a combustion space and defining annular fuel passages 7 between the shrouds and the walls, two annular fuel manifolds connecting the said ducts with the said passages and discharging a layer of fuel over the inside surfaces of the shrouds, the fuel ducts having circumferentially spaced fuel outlets extending radially from one said manifold to the other and discharging into the combustion space, a second air duct, a mixing device interconnecting the second air duct and the outlet of the combustion chamber to mix the air with the mixture of fuel and combustion products flowing from the combustion chamber, and combustion means downstream of the mixing device for burning the fuel in the air supplied through the second air duct.

References Cited UNITED STATES PATENTS MARTIN P. SCHWADRON, Primary Examiner.

D. HART, Assistant Examiner. 

1. A COMBUSTION SYSTEM FOR VAPORIZABLE FUEL COMPRISING, IN COMBINATION, MEANS FOR SUPPLYING LIQUID FUEL, AN ANNULAR HEAT EXCHANGER FOR VAPORIZING THE FUEL, A TURBINE SUPPLIED WITH VAPORIZED FUEL BY THE HEAT EXCHARGER AND DRIVEN THEREBY, AN ANNULAR AXIAL-FLOW COMBUSTION APPARATUS INCLUDING OUTER AND INNER ANNULAR WALLS DISPOSED AROUND THE TURBINE, MUTUALLY CIRCUMFERENTIALLY SPACED RECURVED FUEL DUCTS CONNECTING THE OUTLET OF THE TURBINE TO ONE END OF THE COMBUSTION APPARATUS, THE HEAT EXCHANGER BEING DISPOSED AT THE OTHER END OF THE COMBUSTION APPARATUS FOR LOW OF MIXED FUEL AND COMBUSTION PRODUCTS THERETHROUGH, AN AIR COMPRESSOR DRIVEN BY THE TURBINE, A DUCT CONNECTING THE OUTLET OF THE COMPRESSOR TO THE COMBUSTION APPARATUS ENCLOSING THE SAID FUEL DUCTS AND SUPPLYING AIR TO THE COMBUSTION APPARATUS THROUGH THE SPACES BETWEEN THE DUCTS, OUTER AND INNER ANNULAR SHROUDS WITHIN THE COMBUSTION APPARATUS DEFINING A COMBUSTION SPACE AND DEFINING ANNULAR FUEL PASSAGES BETWEEN THE SHROUDS AND THE WALLS, AND TWO ANNULAR FUEL MANIFOLDS CONNECTING THE SAID DUCTS WITH THE SAID ANNULAR FUEL PASSAGES. 